Mr Hague is concerned that Lady Ashton's attempt to give the EU new security powers will undermine Nato and lead further Brussels demands for extra cash at a time of national defence cuts.

"We are opposed to this because we think it duplicates Nato structures and permanently disassociates EU planning from Nato planning," he said.

"We won't be agreeing to a permanent operational headquarters and therefore we are not able to welcome today's report by Cathy Ashton on this matter."

Alain Juppe, the French foreign minister, praised Lady Ashton's "excellent" proposals for an EU HQ but admitted that British opposition had blocked the move.

Mr Hague suggested that rather than creating a separate EU structure that European governments improved links between national HQs and asked for contributions from military commanders earlier in planning military operations.

Lady Ashton's proposals would have created a permanent staff of 250 military officers and civil crisis management officials with operational control over EU "battle groups", including British troops.

The EU is running a series of overseas military missions, such as a naval antipiracy mission off the coast of Somalia and a Balkans peacekeeping mission.

Lady Ashton defended her proposals.

"This was to fulfil what the Lisbon Treaty was all about," she said. "The position of the British government is the same as the last government. It is not a blow, it was no surprise. It is important to put ideas on the table even if member states decide to reject them."